A downhole pump is used to extract a natural resource such as oil, geothermal fluid, and potable water from a deep well. A typical downhole pump is a vertical turbine pump which has three main parts: the head assembly which comprises the motor for driving the pump, the shaft and column assembly, and the pump bowl assembly. The lower pump bowl assembly comprises the stationary bowl and the impeller for accelerating the flow of the fluid to be extracted, which rotates within the bowl. The shaft and column assembly provides the connection between the head assembly and the pump bowl assembly. The line shaft transmits torque from the pump motor to the impellers and rotates internally to the column. The extracted fluid is transported within the column to the surface.
Vertical turbine pumps have thrust loads acting parallel to the line shaft that include downward forces due to unbalanced pressure forces, downward forces due to the weight of the rotating parts, and upward forces due a change in momentum as a result of the flow though the impellers. The line shaft may be subjected to excessive upthrust forces when the pump is operated at very high flow rates which can lead to various mechanical problems such as deformation of the line shaft, bearing wear, and damage to the impellers by being rubbed against the bowls.
It would be desirable to provide data regarding the position of the impeller in order to determine whether it is liable to be damaged.
The present invention advantageously provides an apparatus and method for accurately measuring the position of a downhole pump impeller, in order to prevent damage thereto.
Other of the invention will become apparent as the description proceeds.